The animal core will provide program project investigators with access to aged rhesus macaques and an extensive biomarker database. A colony of thirty aged female rhesus and additional young control females will be maintained in the California Regional Primate Research Center for behavioral and neuroanatomical studies. The biomarker data base will include daily determination of menses cycle activity, monitoring of reproductive hormone metabolites in the urine, serum hormone levels, and routine clinical parameters such as complete blood counts, serum chemistries, and urinalysis. For study designs which require ovariectomized animals, the animal core will perform bilateral ovarictomies on aged females or young controls, and estradiol replacement, and conditioning for animal handling and transport. Macaque reproductive and physiological parameters will be provided to Core Band made easily accessible to all investigators for experimental analysis.